This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Maize like all other plants lacks a germ line. Late in the life cycle a small number of vegetative stem cells present in flowers differentiate as pre-germinal cells;these cells undergo meiosis to produce haploid spores, which divide by mitosis to form the haploid phase of the life cycle. Given this life cycle, DNA damage that occurs in the vegetative cells could be transmitted to the progeny if it is not repaired;other forms of cellular damage to proteins, RNA, or lipids could compromise plant growth and reproduction if not repaired as well. To understand how integrity of the genome is maintained and how maize responds to continuous damage, two DNA mutagens are employed: UV-B radiation, a natural component of sunlight, and MuDR/Mu DNA transposons. Transcriptome profiling and proteomics are being used to discover the range of acclimation responses to these agents in various somatic and reproductive tissues. Two-dimensional separation (by isoelectric point and by size) is used to fractionate the major proteins of treated and control tissues, providing data on ~3000 resolved protein types. The proteins are classified as unchanged, increased or decreased by specific treatments, and the proteins showing consistent alterations are recovered for identification. All of the protein identification is conducted in collaboration with the UCSF Mass Spectrometry Facility;to date, about 150 proteins have been identified by mass fingerprinting and sequencing. Among these proteins are a number predicted from the transcriptome profiling as well as proteins not previously implicated in responses to either UV-B or transposon-induced genomic damage. The combination of transcriptome profiling and proteomics data are used to determine which signal transduction pathways and cellular processes are involved;verification experiments include genetic analysis of mutants in key processes identified, i.e. by demonstrating that mutants show increased UV-B sensitivity. Current work focuses on elucidating post-translational modifications of proteins that were not altered in abundance by the treatments, followed by identification by mass spectrometry. These studies will likely highlight the most rapid responses to the treatments.